THE PETROGRAPHIC APPROACH TO COAL-LIQUEFACTION

The procedure for quantitative estimation of a maceral liquefaction reactivity is outlined in terms of the regression analysis which takes into account petrographic composition and coal rank. The procedure is based on an additive model for maceral liquefaction and includes a mathematical/statistical analysis of conversion and/or kinetic data for coals characterized by simplified petrographic composition, i.e. by contents of liptinite (exinite), vitrinite and inertinite. The procedure was applied to long contact time liquefaction data for low sulphur high volatile bituminous coals of different rank and to kinetic analysis of short contact time liquefaction data for subbituminous and bituminous coals. On average, inertinite reacts with tetralin three times slower than vitrinite which itself is only half as reactive as liptinite. This is the reason for a decreasing apparent rate constant with extent of conversion in liquefaction of petrographically inhomogeneous coals. The activation energies in liquefaction with tetralin of subbituminous and bituminous coals are respectively 11.4 and 125 kJ mol-1 for vitrinite, and 63.3 and 98 kJ mol-1 for inertinite. Shortcomings and possible modifications of the model are discussed.